Heat sink for chip stacking applications

ABSTRACT

A heat sink is provided for use with stacks of integrated chips. The heat sink includes a thermally conductive body having a heat absorbing section which is inserted within the chip stack, and heat transfer and dissipating sections which are located outside of the chip stack.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to the field of integratedcircuits. More particularly, the invention provides a heat sink for usewith stacks of integrated circuits.

[0003] 2. Description of the Related Art

[0004] As computer manufacturers have attempted to build more powerfulmachines, the use of chip stacks in modern computing applications hasbecome increasingly desirable. The term ‘chips’ used with the presentinvention is intended to include any packaged integrated circuit deviceincluding processing devices e.g. microprocessors etc., memory devicese.g. DRAMS, SRAMS, etc., and the like. In essence, a chip stackcomprises multiple integrated circuit packages which are stackedtogether (back-to-front or back-to-back). The chip stacks may beoriented either in face up position or in a side-to-side orientationwith chip edges down.

[0005] There are a number of advantages to the chip stack configurationover conventional single chip mounting arrangements. In particular, thechip stacks provide a more compact circuit arrangement for computers andother high speed electronic systems.

[0006] In addition, chip stacks particularly allow for more efficientuse of space on circuit boards. The stack takes advantage of relativelyless valuable space above the circuit board, while at the same timeleaving a small footprint on a circuit board or card, thereby increasingthe space available for other components or chip stacks.

[0007] While there are numerous advantages to a stacked chipconfiguration, there are also associated problems. Specifically, largerand larger chip stacks create unique cooling problems. Because the chipstacks contain multiple chips, they generate more heat per unit volume,requiring greater heat dissipation, while at the same time providingsignificantly smaller surface areas which may be used as a heat sink. Inview of this problem, the general response in the industry to the needfor cooling chip-stacks has been to immerse the entire chip-stack inliquid or to operate at greatly reduced power levels. This is often anunwelcome solution because of technical concerns and also because ofcustomer and user preferences.

SUMMARY OF THE INVENTION

[0008] The present invention is generally directed at providing arelatively low cost heat sink for dissipating heat generated within chipstacks (sometimes referred to as ‘chip cubes’, although a cubicstructure is not necessary). The invention provides a heat absorbingsurface between at least a first and second chip within a chip stackwhich is connected to a heat dissipating surface located outside thestack. According to a preferred embodiment, the heat sink includes oneor more heat absorbing sections for respective insertion between chipswithin one or more chip stacks; a heat transfer section for transferringheat away from the absorbing sections; and a heat dissipating sectionfor commonly dissipating heat transferred from the heat absorbingsections.

[0009] These and other features and advantages of the invention willbecome more readily apparent from the following detailed description ofpreferred embodiments of the invention which are provided in connectionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010]FIG. 1 is a plan view of a heat sink of a first embodiment of theinvention.

[0011]FIG. 2 is a side view of the heat sink shown in FIG. 1.

[0012]FIG. 3 is a perspective view of the heat sink of FIG. 1 secured tochips on a chip mounting surface.

[0013]FIG. 4 is a side view of the heat sink configuration shown in FIG.3.

[0014]FIG. 5 is a side view of a first alternative heat sinkconfiguration of the invention.

[0015]FIG. 6 is a side view of a second alternative heat sinkconfiguration of the invention.

[0016]FIG. 7 is a side view of a third alternative heat sinkconfiguration of the invention.

[0017]FIG. 8 is a perspective view of a preferred embodiment of theinvention.

[0018]FIG. 9 is a perspective view of a fourth alternative embodiment ofthe invention.

[0019]FIG. 10 is a perspective view of a fifth alternative embodiment ofthe invention.

[0020]FIG. 11 is a perspective view of a sixth alternative embodiment ofthe invention.

[0021]FIG. 12 is a perspective view of a second preferred embodiment ofthe invention.

[0022]FIG. 13 is a sideview of the second preferred embodiment shown inFIG. 12.

[0023]FIG. 14 is a side view of an alternative embodiment of the secondpreferred embodiment shown in FIGS. 12 and 13.

[0024]FIG. 15 is a block diagram of a processor system in which theinvention may be utilized.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0025] Referring to FIG. 1, a planar heat sink 20 in accordance with apreferred embodiment of the invention will now be described. Heat sink20 is shown including three interconnected co-planar sections: a heatabsorbing section 22, a heat transfer section 24, and a heat dissipatingsection 26. FIG. 2 is a side view of heat sink 20 showing the relativelateral dimensions of the heat absorbing section 22, heat transfersection 24, and heat dissipating section 26.

[0026] Heat absorbing section 22 includes one or more fingers 22 a-22 h,each of which is configured to be insertable between chips of a chipstack. Heat transfer section 24 includes heat transfer elements 24 a-24h. The fingers 22 a-22 h remove heat from the chip stack, which flowsthrough respective heat transfer sections 24 a-24 h to dissipationsection 26. Preferably, fingers 22 a-22 h are of a generally rectangularshape and sized to maximize heat absorption from a target chip'ssurface. As shown in FIG. 1, the width of the fingers 22 a-22 h islarger than the width of the heat transfer elements 24 a-24 h.Alternatively, the width of the fingers 22 a-22 h may be the same,narrower or wider than the width of the heat transfer elements 24 a-24h.

[0027] Preferably, heat sink 20 is comprised of a thermally conductivematerial having a thermal rate of expansion approximately equal to thethermal expansion rate of the stacked chips. In accordance with apreferred embodiment, heat sink 20 is comprised of a metal such asaluminum or copper and may be easily stamped out of plate metal. Inalternative embodiments, it is possible for each of the three sectionsof heat sink 20 to be formed of different materials in accordance witheach section's functional constraints.

[0028] With reference to FIGS. 3, 4, and 8, heat sink 20 is utilized byplacing each heat absorbing finger 22 a-22 h over a first layer chip 30secured on a mounting surface 28 such as a plug-in board having edgeconnectors 27. A second layer of chips is then secured over each heatabsorbing finger 22 a-22 h. Each finger 22 a-22 h may be affixed to thefirst and second layer chips 30, 32 using thermally conductivityenhancing mediums such as a thermal paste or epoxy. With reference toFIGS. 3 and 4, heat sink 20 is shown with each finger 22 a-22 h placedover a respective first layer chip 30 with the heat transfer elements 24a-24 h and heat dissipating section 26 extending away from the locationof the chips 30, 32. As shown in FIG. 8, a second layer of chips 32 isprovided over the first layer of chips 30 with each respective finger 22a-22 h positioned between each pair of first and second layer chips 30,32. As shown, the heat transfer elements 24 a-24 h and heat dissipatingsection 26 are provided outside the chip stack 33 created by the firstand second layers of chips 30, 32. In an alternative embodiment, theheat transfer elements 24 a-24 h may be provide so that at least aportion of the heat transfer elements 24 a-24 h lie within the chipstack 33.

[0029] With reference to FIGS. 3, 4, and 8, the heat transfer and heatdissipating sections 24, 26 are shown provided coplanar with heatabsorbing section 22. As shown in FIGS. 5-7, the heat transfer and heatdissipating sections 24,26 may extend from the heat absorbing section 22at any angle necessary to take advantage of unused space above and belowthe chip stack. With reference to FIG. 5, an alternative embodiment isshown in which heat dissipating section 26 is at approximately a 45degree angle to the heat absorbing section 22. With reference to FIG. 6,an alternative embodiment is shown in which the heat dissipating section26 is orthogonal to the heat absorbing section 22. With reference toFIG. 7, an alternative embodiment is shown in which the heat dissipatingsection 26 is initially orthogonal to the heat absorbing section 22 andthen is bent again be in parallel with the heat absorbing section 22 ata point above the heat absorbing section.

[0030] With reference to FIG. 9, an alternative embodiment is shown inwhich the heat dissipating section 26 is comprised of heat dissipatingfins 34 in order to further enhance heat dissipation by enlarging thesurface area of section 26. With reference to FIG. 10, an additionalalternative embodiment is shown in which the heat dissipating section 26is formed as corrugation waves 36 in order to increase surface area andheat dissipation.

[0031] With reference to FIG. 11, an alternative embodiment is shown inwhich heat sink 27 includes a heat dissipating section 26 in thermalcontact with a pair of heat transfer sections 24, 25 and a pair of heatabsorbing sections 22, 23, which extend along both sides of heatdissipating section 26. As shown in FIG. 11, heat transfer sections 24and 25 respectively contain heat transfer elements 24 a-24 h and 25 a-25h, and heat absorbing sections 22 and 23 respectively contain heatabsorbing elements 22 a-22 h and 23 a-23 h.

[0032] With reference to FIGS. 12 and 13, a second preferred embodimentis shown in which a pair of planar heat sinks 37, 39 are used togetherto dissipate heat from chip stacks 33, 35 positioned on each side ofmounting surface 28. Alternatively, as shown in FIG. 14, a singlecontinuous heat sink 41 may be used to dissipate heat from chip stacks33, 35 positioned on each side of mounting surface 28.

[0033] One particular environment in which the heat sink of theinvention may be used is within a memory module for a processor-basedsystem. In this case, the integrated circuits 30, 32 may be integratedcircuit memory devices such as DRAMS, SRAMS, EEPROM, etc. and themounting surface 28 may be constructed as a plug-in board such as a SIMM(Single In-Line Memory Module), DIMM (Dual In-Line Memory Module),SO-SIMM (Small Outline-Single In-Line Memory Module), SO-DIMM (SmallOutline-Dual In-Line Memory Module), RIMM (Rambus In-Line Memory Module)or other plug-in module, for receipt in a system memory socket.

[0034] A typical processor-based system, which includes the presentinvention formed as a memory module, is illustrated generally at 640 inFIG. 15. A processor-based system typically includes a processor, whichconnects through a bus structure with memory modules, which contain dataand instructions. The data in the memory modules is accessed duringoperation of the processor. This type of processor-based system is usedin general purpose computer systems and in other types of dedicatedprocessing systems, e.g. radio systems, television systems, GPS receiversystems, telephones and telephone systems to name a few.

[0035] Referring to FIG. 15, such a processor-based system generallycomprises a central processing unit (CPU) 644, e.g. microprocessor, thatconmmunicates to at least one input/output (I/O) device 642 over a bus652. A second (I/O) device 646 is illustrated, but may not be necessarydepending upon the system requirements. The processor-based system 640also may include a static or dynamic random access memory (SRAM, DRAM)648 in the form of memory modules of the kind described and illustratedabove, a read only memory (ROM) 650 which may also be formed in the formof memory modules of the kind described above. The processor-basedsystem may also include peripheral devices such as a floppy disk drive654 and a compact disk (CD) ROM drive 656, which also communicate withCPU 644 over the bus 652. It must be noted that the exact architectureof the processor-based system 600 is not important and that anycombination of processor compatible devices may be incorporated into thesystem. Each of the memories 648 and 650 may be constructed as plug-inmodules employing a heat sink constructed in accordance with theteachings of the invention.

[0036] The above description and accompanying drawings are onlyillustrative of preferred embodiments, which can achieve and provide thefeatures and advantages of the present invention. It is not intendedthat the invention be limited to the embodiments shown and described indetail herein. For instance, the present invention is described onlywith respect to stack of two chips stacked vertically. Alternatively,the present invention may be used with any number of stacked chips,which may be stacked in a vertical, horizontal, or in side-by-sidefashion. Accordingly, the invention is not limited by the foregoingdescription but is limited only by the spirit and scope of the appendedclaims.

[0037] What is claimed as new and desired to be protected by LettersPatent of the United States is:

1. A heat sink for stacked integrated circuits, said heat sinkcomprising: at least one heat absorbing section; said heat absorbingsection having at least one planar extending element configured to beinterposed between stacked integrated circuits; a heat dissipationsection; and, a heat transfer section interconnecting said heatabsorbing section and said heat dissipating section, said heat transfersection having at least one heat transfer element connected to arespective planar extending element.
 2. The heat sink of claim 1 ,wherein said heat dissipating section contains a plurality of outwardlyextended fins.
 3. The heat sink of claim 2 , wherein said plurality ofoutwardly extending fins extend the length of said heat dissipatingsection.
 4. The heat sink of claim 1 , wherein said heat dissipatingsection contains corrugations.
 5. The heat sink of claim 4 , whereinsaid corrugations extend along the length of said heat dissipatingsection.
 6. The heat sink of claim 1 , wherein said heat absorbingsection is comprised of a plurality of planar extending elements eachconfigured to be interposed between stacked integrated circuits, andsaid heat transfer section is comprised of a plurality of heat transferelements respectively connected to said plurality of planar extendingelements.
 7. The heat sink of claim 6 , wherein said heat sink isplurality of planar extending elements extend from opposite sides ofsaid heat dissipating section.
 8. The heat sink of claim 7 , whereinsaid absorbing section is comprised of a thermally conductive materialhaving a thermal rate of expansion approximately equal to the thermalexpansion rate of the stacked integrated circuits.
 9. The heat sink ofclaim 6 , wherein at least one heat transfer element is the same widthas at least one of said planar extending elements.
 10. The heat sink ofclaim 6 , wherein at least one heat transfer element is narrower than atleast one of said planar extending elements.
 11. The heat sink of claim10 , wherein at least one of said plurality of planar extending elementsis rectangular.
 12. The heat sink of claim 6 , wherein said heatabsorbing section, said heat transfer section, and said heat dissipatingsection are coplanar.
 13. The heat sink of claim 6 , wherein said heatabsorbing section, said heat transfer section, and said heat dissipatingsection are not coplanar.
 14. The heat sink of claim 13 , wherein saidheat dissipating section is orthogonal to said heat absorbing section.15. The heat sink of claim 6 , wherein at least one of said heattransfer elements is configured so that in use it is located outsidesaid stacked integrated circuits.
 16. The heat sink of claim 6 , whereinat least one of said heat transfer elements is configured so that in useit is located within said stacked integrated circuits.
 17. A heat sinkfor a stacked integrated circuit, said heat sink comprising: a firstportion configured to be interposed between two stacked integratedcircuits; and, a second portion connected to said first portion fordissipating heat.
 18. The heat sink of claim 17 , wherein said secondportion includes a plurality of outwardly extended fins configured toremove heat from said heat sink.
 19. The heat sink of claim 17 , whereinsaid second portion contains areas of corrugation.
 20. The heat sink ofclaim 17 , wherein said heat sink is comprised of a thermally conductivematerial having a thermal rate of expansion approximately equal to thethermal expansion rate of the stacked integrated circuits.
 21. The heatsink of claim 17 , wherein said first portion is comprised of aplurality of rectangular elements.
 22. The heat sink of claim 17 ,wherein said heat sink is substantially flat.
 23. The heat sink of claim17 , wherein said heat sink is not substantially flat.
 24. The heat sinkof claim 17 , wherein said heat sink is configured so that in use atleast of portion of said heat sink is located outside said stackedintegrated circuit.
 25. The heat sink of claim 17 , wherein said heatsink is configured so that in use at least of portion of said heat sinkis located within said stacked integrated circuit.
 26. A method ofremoving heat from stacked integrated circuits, said method comprising:providing at least one heat absorbing section; said heat absorbingsection having at least one planar extending element interposed betweenstacked integrated circuits; providing a heat dissipation section; and,providing a heat transfer section interconnecting said heat absorbingsection and said heat dissipating section, said heat transfer sectionhaving at least one heat transfer element connected to a respectiveplanar extending element.
 27. The method of claim 26 , wherein said heatdissipating section contains a plurality of outwardly extended fins. 28.The method of claim 27 , wherein said plurality of outwardly extendingfins extend the length of said heat dissipating section.
 29. The methodof claim 26 , wherein said heat dissipating section containscorrugations.
 30. The method of claim 29 , wherein said corrugationsextend along the length of said heat dissipating section.
 31. The methodof claim 26 , wherein said heat absorbing section is comprised of aplurality of planar extending elements each configured to be interposedbetween stacked integrated circuits, and said heat transfer section iscomprised of a plurality of heat transfer elements respectivelyconnected to said plurality of planar extending elements.
 32. The methodof claim 31 , wherein said plurality of planar extending elements extendfrom opposite sides of said heat dissipating section.
 33. The method ofclaim 32 , wherein said heat absorbing section is comprised of athermally conductive material having a thermal rate of expansionapproximately equal to the thermal expansion rate of the stackedintegrated circuits.
 34. The method of claim 31 , wherein at least oneheat transfer element is the same width as at least one of said planarextending elements.
 35. The method of claim 31 , wherein at least oneheat transfer element is narrower than at least one of said planarextending elements.
 36. The method of claim 35 , wherein at least one ofsaid plurality of planar extending elements is rectangular.
 37. Themethod of claim 31 , wherein said heat absorbing section, said heattransfer section, and said heat dissipating section are coplanar. 38.The method of claim 31 , wherein said heat absorbing section, said heattransfer section, and said heat dissipating section are not coplanar.39. The method of claim 38 , wherein said heat dissipating section isorthogonal to said heat absorbing section.
 40. The method of claim 31 ,wherein at least one of said heat transfer elements is configured sothat in use it is located outside said stacked integrated circuits. 41.The method of claim 31 , wherein at least one of said heat transferelements is configured so that in use it is located within said stackedintegrated circuits.
 42. A method for removing heat from a stackedintegrated circuit, said method comprising: providing a heat sink havinga first portion configured to be interposed between two stackedintegrated circuits and a second portion connected to said first portionfor dissipating heat.
 43. The method of claim 42 , wherein said secondportion includes a plurality of outwardly extended fins configured toremove heat from said heat sink.
 44. The method of claim 42 , whereinsaid second portion contains areas of corrugation.
 45. The method ofclaim 42 , wherein said heat sink is comprised of a thermally conductivematerial having a thermal rate of expansion approximately equal to thethermal expansion rate of the stacked integrated circuits.
 46. Themethod of claim 42 , wherein said first portion is comprised of aplurality of rectangular elements.
 47. The method of claim 42 , whereinsaid heat sink is substantially flat.
 48. The method of claim 42 ,wherein said heat sink is not substantially flat.
 49. The method ofclaim 42 , wherein said heat sink is configured so that in use at leastof portion of said heat sink is located outside said stacked integratedcircuits.
 50. The method of claim 42 , wherein said heat sink isconfigured so that in use at least of portion of said heat sink islocated within said stacked integrated circuits.
 51. A memory modulecomprising a printed circuit board mounting memory devices, wherein saidprinted circuit board comprises a heat sink for stacked integratedcircuits, wherein said heat sink comprises: at least one heat absorbingsection; said heat absorbing section having at least one planarextending element configured to be interposed between stacked integratedcircuits; a heat dissipation section; and, a heat transfer sectioninterconnecting said heat absorbing section and said heat dissipatingsection, said heat transfer section having at least one heat transferelement connected to a respective planar extending element.
 52. Thememory module of claim 51 , wherein said heat dissipating sectioncontains a plurality of outwardly extended fins.
 53. The memory moduleof claim 52 , wherein said plurality of outwardly extending fins extendthe length of said heat dissipating section.
 54. The memory module ofclaim 51 , wherein said heat dissipating section contains corrugations.55. The memory module of claim 54 , wherein said corrugations extendalong the length of said heat dissipating section.
 56. The memory moduleof claim 51 , wherein said heat absorbing section is comprised of aplurality of planar extending elements each configured to be interposedbetween stacked integrated circuits, and said heat transfer section iscomprised of a plurality of heat transfer elements respectivelyconnected to said plurality of planar extending elements.
 57. The memorymodule of claim 56 , wherein said heat sink is plurality of planarextending elements extend from opposite sides of said heat dissipatingsection.
 58. The memory module of claim 57 , wherein said heat absorbingsection is comprised of a thermally conductive material having a thermalrate of expansion approximately equal to the thermal expansion rate ofthe stacked integrated circuits.
 59. The memory module of claim 56 ,wherein at least one heat transfer element is the same width as at leastone of said planar extending elements.
 60. The memory module of claim 56, wherein at least one heat transfer element is narrower than at leastone of said planar extending elements.
 61. The memory module of claim 60, wherein at least one of said plurality of planar extending elements isrectangular.
 62. The memory module of claim 56 , wherein said heatabsorbing section, said heat transfer section, and said heat dissipatingsection are coplanar.
 63. The memory module of claim 56 , wherein saidheat absorbing section, said heat transfer section, and said heatdissipating section are not coplanar.
 64. The memory module of claim 63, wherein said heat dissipating section is orthogonal to said heatabsorbing section.
 65. The memory module of claim 56 , wherein at leastone of said heat transfer elements is configured so that in use it islocated outside said stacked integrated circuits.
 66. The memory moduleof claim 56 , wherein at least one of said heat transfer elements isconfigured so that in use it is located within said stacked integratedcircuits.
 67. A memory module for a stacked integrated circuit, saidmemory module comprising: a heat sink including a first portionconfigured to be interposed between two stacked integrated circuits anda second portion connected to said first portion for dissipating heat.68. The memory module of claim 67 , wherein said second portion includesa plurality of outwardly extended fins configured to remove heat fromsaid heat sink.
 69. The memory module of claim 67 , wherein said secondportion contains areas of corrugation.
 70. The memory module of claim 67, wherein said heat sink is comprised of a thermally conductive materialhaving a thermal rate of expansion approximately equal to the thermalexpansion rate of the stacked integrated circuits.
 71. The memory moduleof claim 67 , wherein said first portion is comprised of a plurality ofrectangular elements.
 72. The memory module of claim 67 , wherein saidheat sink is substantially flat.
 73. The memory module of claim 67 ,wherein said heat sink is not substantially flat.
 74. The memory moduleof claim 67 , wherein said heat sink is configured so that in use atleast of portion of said heat sink is located outside said stackedintegrated circuits.
 75. The memory module of claim 67 , wherein saidheat sink is configured so that in use at least of portion of said heatsink is located within said stacked integrated circuits.
 76. Anelectronic system comprising a printed circuit board mounting electronicdevices, wherein said printed circuit board comprises a heat sink forstacked integrated circuits, wherein said heat sink comprises: at leastone heat absorbing section; said heat absorbing section having at leastone planar extending element configured to be interposed between stackedintegrated circuits; a heat dissipation section; and, a heat transfersection, wherein said heat transfer section is comprised of at least oneheat transfer element coupled to said heat absorbing section.
 77. Thesystem of claim 76 , wherein said heat dissipating section contains aplurality of outwardly extended fins.
 78. The system of claim 77 ,wherein said plurality of outwardly extending fins extend the length ofsaid heat dissipating section.
 79. The system of claim 76 , wherein saidheat dissipating section contains corrugations.
 80. The system of claim79 , wherein said corrugations extend along the length of said heatdissipating section.
 81. The system of claim 76 , wherein said heatabsorbing section is comprised of a plurality of planar extendingelements each configured to be interposed between stacked integratedcircuits, and said heat transfer section is comprised of a plurality ofheat transfer elements respectively connected to said plurality ofplanar extending elements.
 82. The system of claim 81 , wherein saidheat sink is plurality of planar extending elements extend from oppositesides of said heat dissipating section.
 83. The system of claim 82 ,wherein said heat absorbing section is comprised of a thermallyconductive material having a thermal rate of expansion approximatelyequal to the thermal expansion rate of the stacked integrated circuits.84. The system of claim 81 , wherein at least one heat transfer elementis the same width as at least one of said planar extending elements. 85.The system of claim 81 , wherein at least one heat transfer element isnarrower than at least one of said planar extending elements.
 86. Thesystem of claim 85 , wherein at least one of said plurality of planarextending elements is rectangular.
 87. The system of claim 81 , whereinsaid heat absorbing section, said heat transfer section, and said heatdissipating section are coplanar.
 88. The system of claim 81 , whereinsaid heat absorbing section, said heat transfer section, and said heatdissipating section are not coplanar.
 89. The system of claim 88 ,wherein said heat dissipating section is orthogonal to said heatabsorbing section.
 90. The system of claim 81 , wherein at least one ofsaid heat transfer elements is configured so that in use it is locatedoutside said stacked integrated circuits.
 91. The system of claim 81 ,wherein at least one of said heat transfer elements is configured sothat in use it is located within said stacked integrated circuits. 92.An electronic system comprising a printed circuit board mountingelectronic devices, wherein said printed circuit board comprises a heatsink for a stacked integrated circuit, wherein said heat sink comprisesa first portion configured to be interposed between two stackedintegrated circuits and a second portion connected to said first portionfor dissipating heat.
 93. The system of claim 92 , wherein said secondportion includes a plurality of outwardly extended fins configured toremove heat from said heat sink.
 94. The system of claim 92 , whereinsaid second portion contains areas of corrugation.
 95. The system ofclaim 92 , wherein said heat sink is comprised of a thermally conductivematerial having a thermal rate of expansion approximately equal to thethermal expansion rate of the stacked integrated circuits.
 96. Thesystem of claim 92 , wherein said first portion is comprised of aplurality of rectangular elements.
 97. The system of claim 92 , whereinsaid heat sink is substantially flat.
 98. The system of claim 92 ,wherein said heat sink is not substantially flat.
 99. The system ofclaim 92 , wherein said heat sink is configured so that in use at leastof portion of said heat sink is located outside said stacked integratedcircuits.
 100. The system of claim 92 , wherein said heat sink isconfigured so that in use at least of portion of said heat sink islocated within said stacked integrated circuits.
 101. A memory modulecomprising a printed circuit board having at least a first side and asecond side each mounting stacked integrated circuits, wherein saidprinted circuit board comprises at least a first heat sink for removingheat from stacked integrated circuits mounted on said first side and asecond heat sink for removing heat from stacked integrated circuitsmounted on said second side, wherein at least one of said first andsecond heat sinks comprises: at least one heat absorbing section; saidheat absorbing section having at least one planar extending elementconfigured to be interposed between stacked integrated circuits; a heatdissipation section; and, a heat transfer section interconnecting saidheat absorbing section and said heat dissipating section, said heattransfer section having at least one heat transfer element connected toa respective planar extending element.
 102. The memory module of claim101 , wherein at least one first heat sink is connected to at least onesecond heat sink.
 103. An electronic system comprising a printed circuitboard having at least a first side and a second side each mountingstacked integrated circuits, wherein said printed circuit boardcomprises at least a first heat sink for removing heat from stackedintegrated circuits mounted on said first side and a second heat sinkfor removing heat from stacked integrated circuits mounted on saidsecond side, wherein at least one of said first and second heat sinkscomprises: at least one heat absorbing section; said heat absorbingsection having at least one planar extending element configured to beinterposed between stacked integrated circuits; a heat dissipationsection; and, a heat transfer section, wherein said heat transfersection is comprised of at least one heat transfer element coupled tosaid heat absorbing section.
 104. The system of claim 103 , wherein atleast one first heat sink is connected to at least one second heat sink.